Reloading Questions

I have an odd situation going on with my dreaded .223/5.56 Mossberg MVP. I just tried a new powder and got great ES and SD numbers and alright accuracy with my bullet combination. Anywho, a new phenomenon has reared its head. The fired brass is pushing out the primers. Like the primers are un-seating themselves. It's not over pressure (primers crater and/or punch a hole in them) and all the primers have a good fit and aren't loose by any means. What could allow the primer to push out like that?

I have a theory that the brass isn't actually headspacing properly and the firing pin is pushing the cartridge farther into the chamber making a gap with the brass and the bolt face...

I have a mossberg mvp series 5.56 bolt action rifle. (It is 5.56 not .223). I’ve been shooting it for about 10 years now and it has a minimum of 3,000 rounds through it. I’ve always had to load it with a lighter than usual powder charge because it has a tendency to have primer cratering.

Recently I have revisited loading heavy for caliber bullets (69 - 73 gr bullets) with BL-C(2) powder. Max charge is 26 grains and I loaded down to 24 grains in 0.2 grain increments. I got the 73 gr bullets to go 2700 fps at 26 grains. It’s a 16” barrel.

I did 5 loads of each charge, every single one cratered the primer and all but the lightest load punched holes in 1-2 of the primers causing the firing pin to malfunction (pull the bolt apart and clear the primer obstruction and…

So i was at the range enjoying a nice day. U was shooting my bolt savage model 11 .223.

Shooting 50gr vmax with Rl10x 23gr loads. Second firing for this G.F.L. Brass. The necks all bulged more closer to the shoulder then case mouth. .010" more. Its visibly different. What gives?

I just listened to episode 60 of the Hornady podcast "it's time to answer some questions."

Part of the discussion was about how in their testing, with increased powder charge, they typically saw increased dispersion. I think they said it didn't always get worse as powder charge increased but it never got better.

I'm of the understanding this is because you're increasing the rotational RPM of the bullet, which would exacerbate any out of balance condition whether that's caused by a manufacturing defect or by some reloading process that isn't 100% perfect.

I see some guys shooting some very small groups with pretty high velocities and I'm hesitant to drop charge weight because I don't want ES/SD to increase.

Are any of you guys getting real small groups at or near ACTUAL max powder charge (not book max) or are you dropping it down a hair and accepting a slightly…